This invention relates to a method of assigning time slots in a system comprising a plurality of subscriber facilities connected to a center via a common medium, the common medium being divided into a plurality of frequency or wavelength channels which are subdivided into time slots, as It is also directed to a system as a center as and to a subscriber facility associated with such a method.
In all systems with multiple access to a common medium, the question arises how to control the access to this medium. In radio transmission over the medium xe2x80x9cairwavesxe2x80x9d, for example, the medium is apportioned by international agreements and frequency allocations based thereon. For some other media, too, such as fiber-optic and coaxial-cable networks, fixed allocations have been made. However, at least part of the total capacity must be assigned on demand.
For such cases, it is common practice to assign time slots for the duration of one call. For a variable traffic volume or for a constant traffic volume in an asynchronous environment, it is also common practice to assign to each call a channel within which the respective time slots to be used are then determined by some kind of mechanism.
In assigning a channel to a call, the respective parameters of the calls already assigned to this channel have to be taken into account. It may be necessary to first switch other calls to another channel before a channel has sufficient residual capacity for the new call. Still, an at least short-time bottleneck may occur in a channel due to variations in the traffic volume of the individual calls, while at other times, the same channel is only slightly loaded.
The object of the invention is to manage the capacity of the channels more effectively.
According to the invention, this object is attained by a method of assigning time slots in a system comprising a plurality of subscriber facilities connected to a center via a common medium, the common medium being divided into a plurality of frequency or wavelength channels which are subdivided into time slots, wherein the center assigns time slots to at least part of the subscriber facilities by specifying one channel and one time-slot number for each assigned time slot, that after each time slot used, each subscriber facility involved changes to the next assigned channel, and that each subscriber facility involved sends information in the time slot with the next assigned time-slot number.
The object is also attained by a system comprising a plurality of subscriber facilities connected to a center via a common medium, the common medium being divided into a plurality of frequency or wavelength channels which are subdivided into time slots, wherein the center comprises means for assigning time slots to the subscriber facilities by specifying one channel and one time-slot number for each assigned time slot, and that at least part of the subscriber facilities comprise means for changing to the next assigned channel after each time slot used and for sending information in the time slot with the next assigned time-slot number.
The object is further attained by a center for a system comprising a plurality of subscriber facilities connected to the center via a common medium, the common medium being divided into a plurality of frequency or wavelength channels which are subdivided into time slots, wherein the center comprises means for assigning time slots to the subscriber facilities by specifying one channel and one time-slot number for each assigned time slot.
The object is still further attained by a subscriber facility for a system comprising a plurality of subscriber facilities connected to a center via a common medium, the common medium being divided into a plurality of frequency or wavelength channels which are subdivided into time slots, wherein the subscriber facility comprises means for changing to the next assigned channel after each time slot used and for sending information in the time slot with the next assigned time-slot number.
Thus, all time slots in all channels are used as a common pool. Each time slot is assigned together with a channel allocation.
Further advantageous features of the invention will become apparent from the following description.